Lupan-3-one (5) was irradiated in n-hexane under an argon atmosphere using a high pressure mercury lamp. Besides three seco compounds, namely 10α-(2-formylethyl)-5β-isopropenyl-des-A-lupane (6), 10α-(2-carboxyethyl)-5β-isopropyl-des-A-lupane (8), and 10α-(2-carboxyethyl)-5β-isopropenyl-des-A-lupane (9), two seco-nor compounds, 10α-(carboxymethyl)-5β-isopropyl-des-A-lupane (7) and lactone of 10α-(carboxymethyl)-5α-hydroxy-5β-isopropyl-des-A-lupane (10), have been isolated and their structures have been determined. NMR signals of 10 were examined using Eu(fod)3-d27 as a shift reagent.